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What are the characteristics of the F-16 airframe lifetime?
What limits the lifetime on the F-16 airframe? I assume it is material fatigue, but what kind, and where on the airframe?
Moreover, what exactly happens? What will happen if this problem is ignored? Will the wings break off? Will the airframe collapse or break somehow?
What can be done about this problem? Can the airframe be maintained somehow, repaired, replaced? For how long can this be done, indefinitely, or only up to a point where it is financially feasible?

It is difficult to estimate how long a particular airframe might last. Also, different aircraft might last different amounts of time for esoteric reasons. For example, mercury amalgamates with aluminum and can weaken it. Even a small amount of mercury can significantly weaken an aluminum structural member. Therefore, you might have one plane with some mercury contamination that will not last nearly as long as one free from that accidental contamination.
Also, how the aircraft is used will significantly affect its lifetime. A few high-stress maneuvers can weaken an airframe. Conversely, an aircraft that is babied and lightly driven may last for many decades.
Ultimately, there is no way to predict how long a given aircraft will last. The best thing to do is to observe it and when cracks start to appear, then you know there is a problem.

To compensate for fatigued structural members, it may be possible, but it depends entirely on the scope and nature of the fatigue. If the fatigue is limited to a restricted location, then theoretically that area could be reinforced. The problem is that the complexity of the engineering is such that in most cases it will be cheaper and more effective to simply replace the aircraft.
Usually wear is most severe at the wing roots, so a plane that is experiencing fatigue can potentially be improved by replacing the wings, but the cost of this is pretty significant, so normally you would only see this in an air force that could not buy new aircraft for some reason.

All military aircraft have airframe time limits, and they are mostly related to fatigue. It should be easy to figure out what portions of the airframe are stressed the most -- think of what sticks out the most from the center, and what's connected to that, or what is subject to stress every time the aircraft flies even if it just goes around the patch and lands.
In reality what aircraft manufacturers will do is mount the aircraft or components thereof in testing fixtures and subject them for long periods of time to the types of stresses that they will have to handle in operational situations. For example, airliner wings are mounted on fixtures and subjected to random stresses with hydraulic actuators. They also have to perform tests that test components to the failure point to confirm what engineers thought it would be.
Some airframes can be overhauled and made airworthy again after they have reached their service limits. The USAF is doing that with some 300 F-16 aircraft in Utah. However, that will only add 4,000 flight hours to the service life of the fighter, or 50% of the original 8,000 flight hour service life. Some customers may look at the cost involved in doing that and decide new aircraft are a better deal.


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What is the essential purpose of making three control laws in Airbus aircraft?
Airbus has normal law, alternate law and direct law. What was the need for specifically making each of these three laws? What benefit does each one offer over the others?
Also, why does Airbus degrade to alternate law upon a failure, and then degrade further, to direct law, on landing gear extension? What benefit is gained from this? For example, with a dual hydraulic failure, it goes to alternate law, and then goes to direct law on landing gear extension.

It is pretty simple: if everything works, no malfunctions, no false signals, then the aircraft is in normal law. You have all the stability and protections that Airbus intended the aicraft to be operated with. In real life, the aircraft will be in this state for 99.999% of the time. In my 12 years of flying, I have never encountered alternate or direct law in line flying. Only in simulator training.
If certain things go wrong (malfunctions, detected wrong signals), the flight control computers cannot function properly in normal law. There may be important signals missing to compute the proper reactions to stick inputs or environmental disturbances. For example, if you lose some of the speed signals, or lose flight control surfaces (hydraulic actuation or electric control), the aicraft reverts to a simpler flight law.
You have less protections in alternate law, and no protections at all in direct law. The aircraft reverts to this state, because it cannot guarantee that the protections will work the way they were designed, and they could even do harm (if all speed indications are lost or wrong, a low or high speed protection would make the aircraft unflyable).
Some Airbus aircraft revert to direct law with gear down (A320), and some do not (A330). With direct law, you have -- as the name suggests -- direct stick to surface control. Sometimes, the aircraft goes straight into direct law (loss of all ADRs for example).
There are even more flight control laws, that are not indicated to the pilots. You have flare law (when below 50 ft radio altitude for landing), ground law, abnormal attitude law, mechanical backup...
To sum it up: Airbus has implemented flight control laws other than normal law to cope with malfunctions and abnormal situations.

In case of dual hydraulic malfunction, why could not the aircraft land in alternate law ? what would be the problem to be specific

Dual Hydraulic is a heavy and complex abnormal. The A330 can actually land in alternate law with this abnormal. The A320 cannot, because the flight control computers are not as sophisticated. At the time when the A320 was developed and certified, there were probably not enough resources, processing power or other reasons to program the alternate law to handle this kind of scenario.

But specifically why? The aircraft is able to fly in alternate law with that, why landing becoems a problem? Can you mention anything specific in regards to that ...

Also, you lose a wide range of systems and control surfaces. Which exactly are inoperative or remain operative varies with the type of abnormal. My guess is that the FCCs of the A320 would not be able to handle every possible combination of malfunctions to remain in alternate law for landing. So, as a general rule, whenever you are in alternate law, it will revert to direct law after gear down. Apparently, the A330's FCCs can handle most losses, which is why it rarely reverts to direct law in abnormals.

An example: the aircraft must be controllable in the flare. If the aircraft remained in an alternate law, which does not take into account a reduced pitch authority if you lose one elevator, for example, you would most probably not make a safe landing. In direct law, you have the full flight control surface deflection available and can compensate. Of course, it's difficult to control, but it's the maximum controllability you can get. I guess that the A330 has a more finely tuned alternate law that can better cope with a loss of various control surfaces.

@SachinChaudhary I don't have specifics on the why, but I can give you an idea on how they made the decision to go to direct law. From the development of normal law, they have an exhaustive list of all available controls and signals.  They can systematically remove said control and signal to determine whether safe flight can continue. Out of this extensive list, they can determine which failures that alternate law cannot handle and will switch to direct law. Given that they have access to a working simulator, it is a matter of grunt work to calculate all scenarios.

Firstly I want to say it's not just Airbus FBW Aircraft that has 3 primary FBW laws/modes. Boeing also has 3 modes for their FBW 777 and 787; Normal mode, Secondary Mode, and finally Direct mode. The 777X will be the same. The same is true for the Gulfstream FBW business jets and various other business jet FBW aircraft. As for why 3 modes/laws for these aircraft, I don't think anyone really knows the true answer to that except the engineers who built these planes. The only 2 FBW aircraft I know of that has only 2 primary FBW modes is the A220 airliner (ex Bombardier C Series) and the Bombardier 7500 business jet. Why only those 2 with only 2 primary FBW modes, I don't know.
A FBW aircraft degrades to alternate law (or secondary mode in the case of the 777 and 787) cause the computers would not be able to calculate data accurately to provide flight envelope protections, enhanced flying qualities and stability etc to remain in normal law/mode. If certain things fail or the computers receives faulty data like if the pitot tubes are blocked, it can't continue in normal law/mode as the computers won't be receiving accurate data or lacking certain data so it downgrades to the 2nd lowest primary FBW mode/law (alternate law/mode/secondary mode) where many protections are lost and handling qualities in manual flight are degraded a little bit. As for why the FBW Airbus (only A320 family apparently) dumps you to direct law upon gear extension when in alternate law, according to some Airbus pilots online, alternate law lacks a flare mode where normal law has it. Flare mode memorizes the attitude you had at 50ft and freezes the autotrim when coming in to land and then shortly after, the computers will introduce a 2 degrees nose down pitch via elevator deflection within 8 seconds, where the pilots have to pull back the sidestick to pitch the nose up to flare afterwards which feels conventional as said by Airbus pilots.
Since alternate law lacks flare mode, you're dumped to direct law upon gear extension where the autotrim of the horizontal stabilizer stops to avoid maintaining pitch up inputs when the sidestick is released and elevator deflection is proportional with aft sidestick inputs. According to some Airbus pilots, this would allow the A320 to nose down a little on it's own and then you pull back the sidestick to flare. This also allows the pilot to land the plane like a conventional aircraft like flare mode in normal law. Some Airbus pilots online said it's would be awkward to land with autotrim still operating by the time you had to land so Airbus wanted to give a conventional feel so they introduced flare law and will dump you in direct law if you was in alternate law. That's what I gathered.
I heard the A330 and the rest of the widebody FBW Airbus aircraft would remain in alternate law even if the gear was deployed and I have to assume it's because the computers are more advanced than those on the A320. The widebodies in alternate law I read online would introduce their own slight nose down pitch when the plane is coming in to land, requiring the pilots to pull back to get the feel of landing conventionally.

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A310 wing attachment point details?
Does anyone have an SRM (structural repair manual) or AMM (aircraft maintenance manual) available for the Airbus A310?
How is the wing attached to the fuselage?
What types of bolts are used?  Are they any special type (high-strength/titanium/etc.)?
Where can I find details on the A310's wing attachment points?

Please let us know who's planes you are repairing so we can avoid that airline.

Its not for repairing purpose , I need it for education purpose. Probably if  working in airline that have a310 in the fleet then I'm pretty sure they would have AMM and SRM Available for staff to study .

Well add that information into the question. "I need to know ..." sounds like you have just taken the wing off and let the original bolts roll across the floor and get lost.

Haha, I would accept the  fact that the question I asked is poorly written

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What are these things on the A350's instrument panel?
https://i.sstatic.net/fQy4e.jpg
.
.
On the FCU Panel, there are some buttons or switches that are not on a320s and some older Airbuses except the A380. what's that and what the function?

http://www.smartcockpit.com/docs/a350-900-flight-deck-and-systems-briefing-for-pilots.pdf

These are the EFIS CP (EFIS Control Panels) for the captain's and First Officer ND's (respectively). For example, clicking on the ARPT button will display airports on the relevant ND (Navigation Display, the right part of the left screen, or the left part of the right screen in the image you provided).
It's pretty clear in this close-up photo.
You can see the mentioned controls in the top left corner and the ND display in the PLAN mode (which shows the entire flight plan).
The barometric pressure setting can also be changed using the EFIS CP.
Opposing your comment regarding the A320, The EFIS CP in the A32X (A318-A321)  is also in a very similar location.

Does it have any specific name?

@Mamad, yes, EFIS Control Panels (or EFIS CP). Also included it in the  answer)

@Mamad See my last edit. The EFIS CP is there also in the A32X

yes you are right, the layout has been changed on the newer aircrafts


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Would jet fuel for an F-16 or F-35 be producible during WW2?
I understand that different types of engines use different types of fuel, and as the description of the [jet] tag says, turboprops and jet engines use different types of fuel.
So if – like in the works of fiction The Final Countdown and 1632 – modern aircraft did find themselves in 1940, which aircraft would you readily be able to find fuel for? And which would you have to (re)develop the fuel for?
Let's take the following aircraft as examples:

AH-64 Apache gunship
Airbus EC 135 P2e
AgustaWestland AW101
Boeing 747 (whatever variant is most prolific today)
Lockheed C-130 Hercules
General Dynamics F-16 Fighting Falcon
Lockheed Martin F-35 Lightning II
Bombardier Dash 8

My assumption is that even the turboprops will not be able to use the aviation fuel available.
Which aircraft could have been fuelled "locally" first? And will any fly with 1940 aviation fuel, maybe with an additive?

"turboprops and Jet engines use different types of fuel" No, turboprops have turbine engines just like jets and use the same fuel (typically Jet A or Jet A-1). Piston engines use different fuel...

Turbine engines run on almost anything that can burn, jet fuel is basically kerosene with some additives. Yes that was available in WWII, probably easier to get than aviation fuel. Related question: https://aviation.stackexchange.com/q/13042/21091

@Koyovis, the engines do (and the same cores are often run on natural gas for power generation), but the fuel pumps rely on lubricating properties of the fuel, which gasoline lacks. Easy to get as it is a large fraction of crude oil and was in less demand back then.

Note fuel is probably the easiest of the problems since your logistics tail for weapons and spare parts and the tools to install everything is somewhat lacking.  If you don't happen to have a Nimitz around, I bet you are not going to do very many sorties.  Also note that starting your jet may require special external power, but that could probably be jiggered up in an afternoon.   Absent a single existential threat, the best thing to do would be to study the heck out of it to jumpstart aerospace by a few decades.

@SethRobertson - Aerospace, electrical engineering, radar, computer science....

Take any russian/sowjet aircraft (like a MIG-25 or a MI-24). You can probably fly them on petrol. :-)

For fiction addressing this question see: https://scifi.stackexchange.com/questions/109243/modern-military-jet-goes-back-to-world-war-i

Jet fuel is mostly kerosene, with some aromatic hydrocarbons mixed in for stability, temperature range and the like. You could probably run military jets on pure kerosene if they were magically transported back to WWII, but you wouldn't have to as it would have been possible to make reasonable jet fuel. The Jet-A standard was made in the 50s, and there were no major differences in the fractions available from WWII.
Before it was an engine fuel kerosene was primarily used for heating and lighting, and it was widely used across the world for that purpose in WWII. It still is in some places around the world where electricity isn't available. The aromatics in jet fuel aren't anything special, so it would have been entirely possible to make a jet fuel.
You could go farther back than WWII and still run a jet on raw kerosene as the modern process to distill it from petroleum was invented in the 1850s.

It still is in some places around the world where electricity isn't available and in some places where electricity is available, like Japan, where kerosene space heaters are really common.

They have kerosene in gas station pumps around where I live in the US. If you buy kerosene here, you are getting Jet A minus some additives and the quality control paperwork. The demand isn't enough for refineries and pipelines to carry a separate product.

Where I'm from Jet-A fuel from the bottom of the barrel (not used in case there are some contaminants) are sold as household kerosene. I've been told the primary difference between jet fuel and regular kerosene is that jet fuel is finely filtered to avoid any contaminants that could clog the fuel system

"jet fuel" aka: kerosene, trademarked in 1854...."was first written about in the 9th century" - "During the medieval Chinese Ming Dynasty [(1368–1644)], the Chinese made use of kerosene"

The state of espionage in WWII as it was, the existence and approximate location of the air wing would likely be given away by the sudden diversion of mumble million gallons per week of kerosene to military uses which as you have summarised, would be unusual in the 1940s.

Diesel will also work just fine in a jet engine (and vice versa); it's basically slightly-longer-chain kerosene.  The main difference in practical use is its higher freezing point, but that can be worked with - and diesel, unlike kerosene, was already used in vast quantities by militaries to fuel trucks and tanks and such.

Correct. Kerosene is similar enough to diesel that diesel should work as well

Hydrocarbon cuts that can be used for jet fuel were plentiful during WWII; it was gasoline, especially high octane avgas, that was in short supply.
Greatly over-simplified: the first stage in a refinery is the pipe still which boils the oil, then condenses it into different fractions according to  temperature ranges. Typically a large fraction is "gas-oil" which contains kerosene type oils a.k.a. jet fuel. Some lower octane gasoline is also collected. To make gasoline, the gas-oil goes to the cat cracker, makes some gasoline. Then, some fractions from the pipe still and the cat cracker go to the reformer (expensive in operation because it uses high pressure hydrogen).
The reformer makes the high octane aromatics needed for avgas. No aromatics are needed in jet fuel.
This is the big picture without desalters, alkylation, vacuum pipe stills, cokers, desulfurizers, isomerization, etc.

Because of the critical need for high octane aromatics , the government gave top priority to building reformers. American Oil probably built the most ( Yorktown VA and Texas City, TX). After the war there was not as much need for high octane , cars had about 7:1 compression. Instead of shutting down the reformers, American offered a high octane unleaded gasoline while all others used tetraethyl lead.  Later, Standard Oil- Indiana bought American and started the name "Amoco". Again , because they had the repormers ,Amoco continued to offer unleaded premium ( in the east and south east ).

I doubt that could be done. Even though jet fuel is mostly kerosene, advancements in fuel production technology have focused on lowering the freezing temperature of the fuel, among other things. You could probably get the engine started on fuel made back then, but it would be difficult to keep the engine going at the altitudes aircraft like the F-16 can fly.

"You'd have to stay under 10k feet" and "it can't be done" are vastly different things, though.

Oh sure, @ceejayoz, because staying under 10k is the optimal mission profile for the F-16. Unhuh. :)

If you've managed to get an F-16 back to WWII, you don't really need to be at the optimal mission altitude to destroy everyone else in the air.

@ceejayoz ammunition might be more of a challenge - the 20mm cannon was loaded with 511 rounds, and making more would be difficult.

@JuanJimenez Good thing the question didn't ask about the optimal mission profile for an F-16 then?

Good thing I didn't say that either, did I. LOL! :)

You can get around it by using a "lighter cut" that has a lower freezing point from the still.  The BOMARC ran its ramjets on 87 octane fuel.  Another way is to subject the fuel to a little lower temperature than its mission requirement, freeze out the undesirable fraction, and pour off the remaining liquid for use. The biggest issue was supply, as a large raid with escorts used mass quantities.  The jets, then and now, seemed a little less picky.

It takes time for fuel to freeze to gelling temperature - more time than the mission lasts? 1-K grade kerosene freezes at around −40 °C. I'm downvoting.

@koyovis The science does not support your conclusion at all. The viscosity of most liquids in the kerosene range is low, but as a kerosene cut approaches its onset of freezing, the liquid viscosity normally increases significantly. That affects fuel flow and hence operation of the engine(s), and the kerosene will freeze immediately in the fuel lines when the temperature gets to the freezing point.


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What are advantages and disadvantages of flaperons?
What are some advantages and disadvantages of flaperons? Do they cause some issues or are they top-notch reliable?

The main downside of flaperons is you can't lower them as much as a regular flap because it has to still do its aileron function when "flaps down".  This means the downgoing flaperon has to be limited to its "lift generation" range when the flaperon mixer is moving it to full down flap plus full down aileron, and can't exploit the "drag generation" range of a normal flap because the resulting adverse yaw is extreme and the roll rate drops.
At the same time, the inboard end of the flaperon contributes marginally to roll control, the roll arm being short.  And you are also limited to the use of differential aileron gearing as an adverse yaw reducer due to the need to keep the flap function reasonably symmetrical.
You end up with a flap with limited extension and therefore limited utility as a flap, and an aileron who's inboard end doesn't do much for roll control.  These issues limit their potential effectiveness to being marginally better than a well sized regular flap and aileron.
The principal advantage is you can get a lower overall stall speed because the early high lift range of flap travel is available across the entire span, and you have a much simplified control system since you are combining aileron and flap on one linkage, with some form of mechanical mixing device in the fuselage.
So, like so many things in aviation, they may seem like an ideal solution and have their place, but the limitations and disadvantages are significant enough that a majority of designers prefer to go with the separate flap/aileron.

speaking of downgoing limit, you can also mention the limited design of flaperon compared to flaps (double slotted fowler flaperon would be hard to move from retracted to extended as fast as aileron role demand)

In my personal experience, flying an ICP Savannah fitted with flaperons, they  produce some adverse yaw, and are not as effective as conventional flaps. Flaperons have, nevertheless, the advantage of a simpler construction and simpler control linkages.


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What is the purpose of these labels on an aircraft's wings?
During a flight on an Airbus neo I was looking at the wing on my left, and noticed a set of labels on it. A few can be seen in the below image:

(The third one on the right is not readable, I was focusing on capturing something else.)
After a bit of working on it I think I found part of the pattern, with letters starting from A in the front of the engine and going B, C, D, etc. while moving farther from the front, and R, L and T standing for Right, Left and Top.
Now, while building a Lego plane set it could absolutely make sense, or maybe if you buy a plane from IKEA... But why on a real life aircraft? Just for something like visual inspection after build?

I think the letters are used during build, just to make sure everything is in the right place.

who flagged this as duplicate? O_o OP is using the same photo, yes, but the question is obviously about a different thing.

To be honest, no LEGO planes have any of these labels at all. :P I build plenty of them and I have seen none with such.

Closer than you may think: notice that these panels all have fasteners visible-- these panels are removed frequently for engine work.  The labels are there so that the maintenance crews can both more easily reattach the panels, and so when they're inspected (again as part of maintenance) you're can quickly confirm that everything is in the right place.
When you have a plane in parts, all the panels start to look very similar lying on a workbench... Having the labels makes things more efficient and safer.

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On an IFR Low Altitude Chart what does this symbol mean?
I read the information below in the aeronautical chart user's guide. I have several questions.

On the third line - Why is there an ICAO identifier for a U.S. & Alaska low altitude chart? I thought ICAO was for international flying?
On the fourth line it says '0' and '*' but there is no explanation. What do these two symbols mean?
On the fifth line it says there is a part time frequency, I assume because the tower is part time based on line three. So if this is the case, why does it need to say part time twice?

CITY - City
Airport Name - Airport Name
(APT) (ICAO) [D]* - Airport Identifier, ICAO Location Identifier, Class D airspace with far 93 special requirements operating part time
280 0* 43s - Airport elevation, unknown symbol, runway length (soft field)
(A) *109.8 - ATIS, Part Time Frequency

FAA charts are international charts to a Canadian pilot... 0* (actually more like (L)* ) is in the legend, it means pilot controlled lighting - part time or on request.

① - ICAO ID
As indicated, will be used for OCONUS airports only (overseas), e.g. Guam has a 4-letter ICAO designator:

② - Symbol with circle: Lighting

An "L" following the elevation under the airport name means that
  runway lights are on during hours of darkness. A circle around the "L"
  indicates there is Pilot Controlled Lighting. A star beside the "L"
  means the lighting is less than continuous.

(Source)
This is part of the legend, but there is no lead line.
③ - ATIS available part-time
This is not the tower frequency (as your question seems to assume), but the ATIS frequency.
This information is not redundant, the ATIS may be available full time for an airfield open part-time. This is the case for Grand Junction Regional in the snapshot above.

Hi thank you. I wasn't asking about the L symbol within the circle, I was asking about the 0*

Ok nevermind, I do see there is a very faded L within the circle. That is why I was confused. Very difficult to see.

ICAO identifier is given for airports outside contiguous US. From FAA National Airspace System:

Airport Information
Airport information is provided in the legend, and the symbols used for the airport name, elevation, and runway length are similar to the sectional chart presentation. ... FAA identifiers are shown for all airports. ICAO identifiers are also shown for airports outside of the contiguous United States.

The symbol in the fourth line is not a zero, but rather the letter 'L' with a circle over it. It represents the avialbility of pilot controlled lighting, and should be clear from the following image from this document

The explanation for '*' is given just for completeness there is an unidentified one in the fourth line.

"ICAO identifier is given for airports outside contiguous US". On the screenshot I posted it says "U.S. and Alaska low altitude chart". So why would it need an ICAO if it depicts airports within the U.S.?

@jskypilot contiguous US  doesn't include Alaska. As the chart depicts US and Alaska, ICAO identifier is given.

In the continental US, an airport with an ICAO identifier is generally the same as the 3-letter FAA identifier, with the letter "K" in front.  (Note, not all airports with an FAA identifier have an ICAO identifier, and the FAA 3-letter identifier won't always match the IATA 3-letter identifier... almost always but not quite. Branson MO and Sawyer MI have IATA/FAA mismatches.) Elsewhere, such as Alaska, the FAA identifier for the airport may or may not match so closely. Anchorage International is ANC (FAA) and PANC (ICAO), but Elmendorf AFB is EDF for the FAA, but PAED for ICAO.  So in Alaska and Hawaii, it's very helpful to list both the 3-letter FAA identifier and the 4-letter ICAO identifier as they may or may not be similar.

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How does a horizontal situation indicator (HSI) work?
I am trying to understand the Horizontal Situation Indicator. To my understanding there is a slaving transmitter, usually in a wing (the left wing in the Piper Archer and Seminole), which sends information to a flux gate, which then sends information to the compass card in a slaved HSI. Is any of that correct? Are the slaving transmitter and the flux gate separate components?

Your understanding is partly right. Usually HSI indicators are associated with a slaving transmitter that includes the flux gate (the magnetic sensor), but also other elements such the directional gyro unit and a slaving control.
So a typical system will usually include the below components (there are different designs, so check the characteristics of the equipment in your aircraft):

The Horizontal Situation Indicator (HSI) is the panel mounted cockpit indicator that provides a comprehensive display including usually at least heading, course, and glide scope. The heading indicator of the HSI is a remote indicating compass that gets its information from a remote slaving transmitter.
The magnetic slaving transmitter includes the flux gate that is the magnetic sensor itself, and some electronics to send the heading information to the directional gyro and HSI. This transmitter and its associated flux gate is usually located in a wingtip to minimize as much as possible magnetic interference.
a directional gyro unit that is usually remote mounted. It is using its internal gyroscope to keep and provide a stable heading reference during turns. This gyro unit is driven/slaved to the slaving transmitter.
The slaving control is panel mounted and allows to selected either "slaved gyro" or "free gyro" mode. Usually, the system is in "slaved gyro" mode and will be slaved automatically. In "free gyro" mode, a slaving meter indicator displays the difference between indicator display and earth's magnetic field, and it is possible to align manually the switch using clockwise or counterclockwise buttons.

The manual of the Bendix-King KCS 55A provides a good introduction to HSI design and operation.

Garmin and others now make electronic HSIs. No more spinning mechanical gyroscopes. A magnetometer is installed in the wing or tail someplace not influenced by magnetic fields caused by current flow in wires.
Garmin indicates

GMU 11 is an affordable, microprocessor-based magnetometer. It can be used to accurately sense the Earth’s magnetic field alignment and provide this data to compatible ADAHRS processors for use in referencing aircraft magnetic heading. In essence, the magnetometer acts as an electronic compass, showing the ADAHRS which direction the aircraft is facing in relation to magnetic north.
Unlike conventional flux valve systems, which detect only the horizontal component of the Earth’s magnetic field, the GMU 11 magnetometer provides full 3-axis vector measurements for the most precise digital indication of magnetic field strength and direction.
ADAHRS components used on our popular G3X, G3X Touch and G5 electronic cockpit displays can use comparative inputs from GPS, magnetometer and air data computer information to achieve new levels of integrity, reliability and precision in digital flight reference.
What’s more, because it’s an all solid-state design, GMU 11 offers low power consumption as well as easy installation and calibration. On most aircraft, GMU 11 is mounted in a separate remote location from the ADAHRS and other electronics — typically outboard in the wing, tail section or vertical stabilizer — to minimize any external magnetic interference.

and

Rock-solid Attitude Reference
When configured as a primary attitude indicator, G5 uses solid-state AHRS reference to provide smooth, steady and reliable horizon-based pitch and roll indications. In addition to aircraft attitude, G5 will also support display of airspeed, altitude, vertical speed, slip/skid, turn rate, configurable V-speed references, barometric setting and selected altitude — as well as visual alerts upon arriving at a preselected altitude. A built-in GPS receiver provides highly accurate groundspeed and ground track readouts. Plus, a dedicated rotary knob on the unit allows for easy adjustments to altitude bugs and barometric pressure settings.
Gain A Clearer Sense of Direction
To provide even more situational awareness, G5 is also approved for installation as a replacement heading indicator/directional gyro (HI or DG) or horizontal situation indicator (HSI) in your panel. When paired with an affordable GMU 11 magnetometer, GAD™ 29 navigation data interface and select VHF Nav/Comms or GPS navigators, G5 can serve as your primary reference source for magnetic heading, VOR/LOC guidance and/or GPS course guidance — as well as providing distance and groundspeed indications. The unit displays both vertical and lateral GPS/VOR/LOC course deviation when available. And you can use the G5 instrument’s rotary knob to easily make and adjust course selections — or to control heading bug settings in DG installations. For added system integration, a single magnetometer can supply heading information to 2 G5 units simultaneously. Additionally, G5 can provide heading output to select third-party autopilots (with GAD 29B).


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When is compressibility a problem for a pitot tube?
One of the errors for a pitot tube is 'compressibility.' However, I don't understand this in detail. I get that the ASI will read slower because the ram air is compressing against the air already in the pitot tube. My question is when does this happen? What would cause this?

I am certainly no expert, and I look forward to learning more by reading the answers, but isn't the ram air compressing against the air already in the pitot tube exactly how it measures air speed in the first place?

@FreeMan No. It measures the lower dynamic pressure due to the velocity of the fluid in the tube (Bernoulli's principle). They work just as well (or, given the premise of this question, better) in water, which is incompressible.

In subsonic flow, a pitot tube measures the total pressure $P_{0}$, while a static port measures the static pressure $P$. For very small Mach numbers, we can use the incompressible form of Bernoulli's Equation for determining the speed.
As there is no energy due to compressibility, the density $\rho$ is constant. This means that along a streamline,
$\frac{P}{\rho} + \frac{1}{2} v^{2} + gh = constant$
Neglecting gravity, we have,
$\frac{P}{\rho} + \frac{1}{2} v^{2} = constant$
Using this, we can determine the velocity as
$v = \sqrt{2\frac{P_{0}-P}{\rho}}$
This equation, however does not take the effect of comprehensibility into account. While at low speeds this is not a problem, this causes an error as the Mach number increases above ~0.3. As the speed increases above this value, the term $\frac{1}{2}\rho v^{2}$ no longer gives the difference between the Total and static pressure.
In case of compressible flow, neglecting gravity we have,
$\int_{P_{0}}^{P}\frac{dP}{\rho} + \frac{1}{2} v^{2} = constant$
along the streamline as $\rho$ is no longer constant.
For adiabatically expanding gas, we have,
$\frac{P_{0}}{P} = (1 + \frac{\gamma-1}{2} M^{2})^{\frac{\gamma}{\gamma - 1}}$
where $\gamma$ is the specific heat constant and $M$ is the mach number. In this case, the velocity can be calculated as,
$v = \sqrt{\frac{2 \gamma}{\gamma - 1} \frac{P}{\rho} [\frac{P_{0}}{P}^{\frac{\gamma - 1}{\gamma}}-1]}$
This difference gives rise to the error, which is positive i.e. compressibility error produces ASI readings that are too high. In terms of the pressure ratio, the error is more than 8% as the aircraft approaches transonic speeds. The following image shows the difference in pressure ratio between readings using assumptions of incompressible and compressible flow.

Image from Mechanical Measurements and Metrology - Measurement of Fluid Velocity by S. P. Venkateshan
Basically, the issue is with the assumptions in the method use to calculate the velocity- for low speeds, we assume that the density is constant, which is clearly not the case as the speed increases. Usually, M = 0.3 is taken as the cutoff point.

"does not take the effect of comprehensibility into account" - are you talking about your answer in general, or the equation?


text:
What does "Clear Of Clouds" mean in reference to Class B Airspace in the United States?
Does "clear of clouds" mean you cannot touch a cloud or does it mean that that Class B airspace must not have any clouds in it?

What is the full context?  Did you read this in a briefing? Receive it as an Instruction from ATC?

Related: What does “clear of clouds” mean in FAA FAR part 103?

That specific phrasing means that you can't touch a cloud. See the VFR minimums in 14 CFR 91.155, where it says:

no person may operate an aircraft under VFR when the flight visibility
  is less, or at a distance from clouds that is less, than that
  prescribed for the corresponding altitude and class of airspace in the
  following table [...]

The table lists the "distance from clouds" in class B as "clear of clouds".
You can also find it in the AIM section 3-2-3 on class B airspace, and in other sections about SVFR, visual approaches etc. where a requirement for those procedures is to remain clear of clouds.
The actual cloud cover in the class B airspace is reported by METARs and ATIS.

It means that the pilot should not touch the clouds in VFR. From CFR 91.115:


text:
What aircraft did this canopy come from?
This canopy was found near Wetumka, Oklahoma in a small creek running through my best friend's property. The canopy is about 12 feet long. Can anyone tell me what aircraft it came from, or who I could contact to ask?
A loving cup from 1906 dedicated to a Miss Grace Walling Spore from the USS Alliance Navy Ship was also found in same creek recently. I contacted the family myself and they knew nothing about the loving cup or any crashed plane that may have been carrying it.

Here is another picture... I do not know if was in a crash.

It could have washed down creek I suppose, but why would a jet canopy have been in a creek? I am searching for what kind of craft it belongs to.

Location: A creek in Wetumka, Oklahoma
Rumored date/pilot: 1944 / Loyde Christian
Object length: ~12 ft

@BrendaSeitz It is quite difficult to make out anything from this image alone. Do you have any other photos from another angle perhaps?

Tentatively I'd suggest a B47 - although there's nothing near you on this database of crashes http://okwreckchasing.org/database.htm

Why is everyone assuming a crash? Couldn't it have just been moved there?

All -- This is not a discussion forum.  Please move all of this to chat if you could: http://chat.stackexchange.com/rooms/12036/the-hangar

Is it possible to get a closer look at the canopy without disturbing it? There may be part numbers on the metal frame (inside or outside) that could be clues as to what type of aircraft it is.

Please do not vandalize your own posts. If you really want to delete it, either hit the delete button, or flag it and ask a moderator to delete it for you.

if your rumoured date is correct, it won't be a jet. If your rumoured name is correct, a FOIA request to the USAF might yield information.

Can you provide any more details about what the link is between the rumored date/pilot and the object?  Also, what is the metallic plate that you are holding, and was it attached to the object? I agree with @PartyArk, it bears a striking resemblance to the canopy from a B-47.  Finally, the canopy frame should be a serialized part.  IF you can find an S/N that would go a long way.

@tiimas,  the plate is off the canopy,  and the only thing with numbers on it, also found another piece of the plane...I can't find any info  on a crash, but other things like silverware from the uss Alliance has been found along with the loving cup.  I assume that stainless steel plate is the serial number.? any help would be helpful. thank you

You've mentioned that the canopy is about 12' long. Can you get an approximate measurement of the width, as well? It looks like one half is pretty well buried (I'd suggest leaving it that way until you know what you've got your hands on) so maybe see if you can get a measurement from edge to center then double it. A height measurement may help, as well.

Sending your pictures and those dimensions to the Public Affairs Officer at Tinker AFB in Oklahoma City might get you some help, as well. It may not be an Air Force jet, but I'd imagine there are some plane geeks on the base who may be able to identify what we haven't been able to.

This canopy probably came off a Boeing B-47.

I do know of at least two mishaps involving B-47s in Oklahoma but both occurred in places other than Wetumka.  I'll do a little more investigating on this.
Another possibility is that the previous landowners acquired this part as scrap at some point and left it there on their property for whatever reason.

Thank you so much, some Sterling silver from 1906 was also found, near this canopy

I don't know if the two are related.

We read somewhere a plane carrying a silver set...tiffany loving cup from 1906  was on plane from new York going to okc. Google info on  john walling spore and Grace walling spore. This cup we found was dedicated to her. It's like the plane was carrying artifacts to a museum,  we also found a rock carving ....old,   by canopy.  Not in wetumka, more like henryetta ok is where it was found.  Any help you can give is helpful....

And the plane was flying this stuff in 1944 I think

Well if it's a B47 which this canopy came off of, it wasn't flying in 1944.

Hmmm. Thank you, any help is appreciated,  I never knew for sure it was 1944....

A B-47's canopy has glass for all three segments. The one in this question looks like it has metal for one of the end segments (presumably the back).

Those photos don't look like metal; it's just discolored plexiglass

A B-47 from Witchita KS broke apart over Tulsa OK March 13 1958.  Its canopy would have to have been transported after the crash to get to Henryetta OK.  ... but there isn't enough data to say that this a B-47 canopy.

It looks like one of the F series. The oldest aircraft I can find with a canopy like this is the F9 Cougar, though other aircraft in the series also use this kind of canopy.

thank you....do u know of one crashing going from new York to okc oklahoma?  with sterling silver from the uss alliance  dated 1906.  the plane parts are around henryetta oklahoma in a creek bed....the tiffany loving cup dedicated to grace Wallace  and some sterling silverware has also been found..just trying to gather any info on pilot. or crash...if you can help me...all I have is phone Internet.

It would help to post a picture of the F9 to compare with the pictures in the question and point out the similarities.

This is a pic of one, best shot I could find of the canopy, looks like it is sectioned the same way as the one you found, but the canopy varied over the different sub-models of the F9, so may be a bit different link

@jakefaulkner thank you, I agree that's the aircraft...found another piece of it with the grey star


text:
How does the load transfer from a prop to the airframe?
I was just watching this video...
Restoration and startup of a Wright 1820 Cyclone
...and it got me thinking: a propeller shoves back air, and this creates a forward force on the prop. The prop attached to a shaft, and the prop is tugging on the shaft. Both the shaft and the prop are rotating.
The airframe on the other hand is (relatively) stationary. Yet the airframe depends on the rotating prop to pull it in the desired direction of trust.
This means there is an interface somewhere, between the rotating shaft and the rest of the engine, and that interface transfers all the thrust of the propshaft to the engine, and then the engine in turn transfers that force to the air frame.
That to me sounds like the mother of all bearings! What does such a bearing look like?! Or is there some other mechanical principle/device in play?

Your car has equally impressive thrust bearings, what do you think turns the car when you round a sharp corner?

The engine mount is an important component that transfers the prop thrust to the airframe. It's clearly visible in this photograph of a fast and powerful plane, a  Bf109. Of course, bearings transfer thrust between the rotating and static parts. That is common to all engine-propelled vehicles, ships, cars, planes... The main thrust load, in the picture showing the turbofan, is taken by the tapered roller bearings.

Also, it would be nice to highlight the engine mount and bearing locations - not everyone is familiar enough with what's under the hood to instantly recognize it...

@FreeMan Well the engine mount even I can see here; it is the light grey-green frame that is "hugging" the big black engine block. But what I was wondering (I have edited the post to clarify) is how the prop transfers trust to the stationary parts of the engine.

The tapered roller bearings, as answered above already.  The shaft pulls forward on the inner bearing housing, the rollers transfer the pulling to the outer bearing housing which push the engine/airframe forward. The rollers let the two parts move independently. More on the bearings here  https://en.wikipedia.org/wiki/Tapered_roller_bearing

Cars are different from planes and ships, and don't need (as much) taper in the bearings - at every stage from crankshaft to road contact, it's pure torque.  But propeller-driven machines need that thrust bearing in order to provide transfer of axial thrust along the shaft.

@TobySpeight - When a car rounds a corner, there are great sideways forces acting upon the wheels (along the axle), which must be transferred to the chassis somehow.

Good point @Rainer


text:
Do the F-16's leading edge flaps lock up at +2° when the aircraft as a whole is supersonic, or when the airflow over its wings is supersonic?
My question is: do the leading edge flaps lock upright when the aircraft as a whole is supersonic, or when airflow over  wings of the aircraft is supersonic?

Are you referring to slats or flaps on the leading edge?

The F16 has  only LEF's (Leading Egde Flaps),for maneuvering .For  landing use the  flaperon s -TEF (trailing edge flaps)

To those who voted to close, what is unclear about the question?

@GeorgeGeo F-16 LEF's are lowered for landing too (high alpha). Check out any picture of an F-16 landing for a reference.

Trust me I know that ,but the question is about the upward trend of the LEF's

There will still be airflow over both the body and the wings of the F-16 or any other aircraft when it flies supersonic.
Moreover, the F-16 features a blended wing-body which makes it hard to strictly separate the two. The body of the aircraft produces some amount of lift. Your question seems to ask if this lift is required, at supersonic speeds in particular.
I believe the F-16 could still fly if one was made without having any lift produced by the body itself and probably fly at supersonic speed, but this is sheer conjecture.
Perhaps you will get a more satisfying answer if you clarify the question a bit?

AlphaCentauri Not talk about the lifting forces here just control laws which programming the leading edges movement


text:
Does the F-16's neutral stability also extend to the negative-G flight regime?
If an F-16 pilot pushes the stick forward hard enough to send the aircraft into negative-G flight, does the jet tend to accentuate the new flightpath, requiring the pilot to counter that, or not?

The F-16 is unstable at low speeds, and stable at higher Mach numbers. It has a flight control computer though, which stabilizes the aircraft using the feedback from pitch rate (so from the view of the pilot an F-16 acts similarly as a stable aircraft). This applies to both positive and negative attitude disturbances, so for both + and - G loads perceived by the pilot.

Thanks ,this instability translate into the quick response in pitch up and down or only up ,this is my question ?Your answer  is accepted.

The stability of the aircraft depends one the derivatives of state variables (velocities and rates). In a normal flight regime (not near stall) these are continuous functions, so the (in)stability will work "both ways". Here you can learn more about the flight dynamics of the F-16: http://home.sch.bme.hu/~xtrykyx/diplomaterv/Egyeb/F16Manual.pdf

Thank you  for your time.


text:
Why do we say certain things three times (e.g., "Mayday, Mayday, Mayday"), rather than two or four?
Repetition is a key characteristic of communication in the control tower, cockpit, and control room.  Some phrases, like "Mayday" get repeated. The speaker says the same thing three times. We know this is for redundancy.
Why exactly three times?
Why not twice or four times? Is there research suggesting three is the most effective number, or is there a historical reason for the convention?

It sounds like you're asking why three, rather than two or four. In other words, you're not just asking "why do we say it three times"; you're asking "why is three the number of times that we say it". Is that right?

That literally means the exact same thing.

For the same reason as Beetlejuice.

@RyanMortensen No, there's a difference in emphasis. The questions "Why do we say it three times?" and "Why do we say it exactly three times, rather than two or four?" are different questions that invite different answers. If you said "It's for redundancy", that would answer the first question, but not the second.

Somewhat related

@TannerSwett having to change what you had originally put in quotes in order to make a rebuttal proves my point.  Another thing is that no one here seems to have implied that we might opt to say it "about three times".  You can't say it 3.64 times or some other fractional figure, so it's either 3 or its a different integer.  If I say I have two dogs, that means I have exactly two dogs, all day every day.  It never implies that I have 1 or 3 dogs or anything other than exactly two.

Five is right out.

One reason that comes to mind is in case another pilot on the same frequency keys in right in the middle of your urgent broadcast.

https://en.wikipedia.org/wiki/Repetition_code

@HenningMakholm - I joined this community just so I could up-vote your comment :)

@TannerSwett question edited to provide clarity / answer your question: why is it exactly three times?

@RyanMortensen: If you're shouting 'Mayday', you're quite likely to say it  3.64 times or other similar fractional number. It's a clear signal to the ground crew to dispatch search/rescue instead of trying to guide you to a safe landing.

Rule of three. If advertising people believe in this, pilots ought to. Mayday is something I'd want to effectively and compellingly communicate, after all. I don't know enough about the history of critical commands to answer, but it's possible this could provide a cultural context.

@RyanMortensen His point still stands even with his original quotes; "it's for redundancy" would answer "why do we say it three times?", but not "why is three the number of times that we say it?".

As a corollary, consider this quote by Ian Fleming, writing about a certain Commander Bond R.N.,  in his novel Goldfinger... Once is happenstance. Twice is coincidence. Three times is enemy action.

This question might get a better answer if asked in a linguistic context rather than an aviation context. The aviation reason to repeat the word is for redudancy and to convery urgency. The reason to say it exactly three times I don't think comes from Aviation, but comes from human behavior and language. When playing pretend, kids often shout things like "help help help" or "Danger danger danger" exactly three times. There are many other examples of this such as Sunday! Sunday! Sunday!

Procedure calls for the mayday distress signal to be said three times in a row so that it won't be mistaken for another word or phrase that sounds similar under noisy conditions. The use of Mayday dates back to 1923 when it was first used because it sounded like the French word m'aider, which means “Help me." In those early days of radio it was necessary to repeat things sometimes because of interference on the frequency from various potential sources.
The "rule of three" is rooted in research conducted in 1890 by Hermann Ebbinghaus, a German psychologist. Ebbinghuas studied how many rehearsals were necessary for his test subjects to memorize a list of nonsense syllables. He came up with three as the optimal number, and that became a rule of thumb in many other things, such as advertising.
Here's a cool video that adds information on Mayday and Pan Pan.

Just a small correction, it is "m'aidez"

@infinitezero Oui ! "M'aidez!" is an imperative meaning "(You) help me!" However, "m'aider" means "to help me", e.g. in a full sentence "I would like someone to help me" (Je voudrais que quelqu'un m'aider).

@CJDennis Note that "Je voudrais que quelqu'un m'aider" is incorrect, it would more likely by "Je voudrais que quelqu'un m'aide". On the other hand, "I would like someone to come help me" would be "Je voudrais que quelqu'un vienne m'aider". (Also "M'aidez!" feels very strange to me. "Help me!" would be "Aidez-moi !")

@Rafalon I don't think I (or anyone else I know) would say those things. As you say Aidez / aide moi would suffice rather than such a long sentence :)

@Cloud Sure thing. I should have made clear that my point is: "m'aidez" is incorrect unless maybe in very old French (I'm French and I've never seen a sentence including it), and "m'aider" must follow a verb ("Venez m'aider")

@Rafalon 's comment is correct.

On second thought, "m'aidez" can be used here "if you help me" -> "si vous m'aidez" but this is not imperative

@Rafalon I think in Canada also it's a bit different, thanks for your help also :)

I think if you're in a situation where a "m'aidez" or whichever is required, you're probably less concerned about grammatical correctness...

Let's ask https://french.stackexchange.com/ !

Yep, the critical commands are repeated 3 times.  This ensures there is ABSOLUTELY zero doubt in anyone's mind (especially on a big crew airplane) of what needs to be done in a critical situation.  It also standardizes these criticalities across different aircraft and aircrew cultures.  "Bail out, bail out, bail out"  "Eject, eject, eject"  "Abort abort abort" "Pan-pan, pan-pan, pan-pan."  I was 27 years a USAF pilot, and this is how the training has worked for over 50 years.  I only saw these terms used 2-3 times, but it certainly gets your attention and amps up the sense of urgency.  A little history:  back in the day of very poor radio communications, it was necessary to repeat to "get someone's attention" or in the event a single "mayday" didn't come across when the transmit button was pressed.

Need clarification. Does emergency "pan" only mentioned 3 times? I heard a senior commercial pilot said that it must be mentioned six times as it only 1 syllable: "Pan-pan, pan-pan, pan-pan".

@AirCraftLover I believe this is is correct.  I read a pronunciation manual that described it as "Pahn-pahn", so that would be one iteration, not two, so you're right. 3 pairs of two "pan"s.

@AirCraft Lover If you take a look at historical editions of ITU's Radio Regulations, and compare it with current, you'll be able to see that there's been a change. The urgency signal was changed from "pan" to "pan-pan". Therefore, it is repeated 3 times, and not 6, but the signal itself has word pan two times in it now.

Seems to be specific to messages over a potentially unreliable communication channel; the (shouted) brace instruction for passengers is just 'brace brace'. Although that instruction is repeated continually.

The question does ask about research and historical convention on the number of repetitions.  No answer has addressed this part of the question.  Whether there is research, there is definitely historical convention about saying things three times for emphasis, that goes back thousands of years.

I am not a pilot. I just heard what said in this video. May day and Pan pan. https://youtu.be/UWpwl-NPnrM

"Pan-pan" is two words in the same way that "may-day" is two words. Syllables would be more accurate.

I agree with @JdeBP  -- since the dawn of radio telephony (or telegraph), is there historical evidence for why it is repeated exactly three times.

This doesn't answer why they say it ** 3 (three)** times and not four, five, two, or seven times.

The method is also used to make otherwise critical commands "less critical" ("Exercise! Exercise! Exercise!") - which is of course also critical in itself ...

There are no instances in normal conversation where the same word is repeated three times consecutively. In order to prevent a critical command or order from being issued or heard accidentally, a command is given three times in order to verify that it is being given intentionally.
Going to the moon? “Launch! Launch! Launch!”

This doesn't seem at all sensible, since any given phrase could be only heard once by the receiver if e.g. the first copy was snapped by a button delay and the second lost in static. The answer by Scotty provides the much more sensible historic basis: three times for redundancy.

This doesn't answer why they say it ** 3 (three)** times and not four, tow, five, or seven times.

do you have sources for your statements?

"Tora! Tora! Tora!" apparently supports this claim.

I assume it's for redundancy. Assuming the voice signal is very noisy, the listener might hear two different things, the first and second time. The third repetition can then be used to decide which of the two versions heard is more likely to be the correct one.
Majority voting with three signals is very common in redundant systems. In computing it is called TMR (triple modular redundancy).
https://en.wikipedia.org/wiki/Triple_modular_redundancy

"I assume". you got any source?

Because human brains are slow and easily distracted?
The first time you heard it - you started listening.
The second time you heard it - you started listening properly, because you know it's important
The third time confirmed you heard what you thought you heard?

This is just my unresearched perception of what's going on, and why we naturally settled on saying thing 3 times when it's imperative that it's heard properly.

Wouldn't this imply also that a large number of initial calls to various air traffic controllers would need to be repeated? The fact that that's generally not necessary would seem to suggest that your perception is, if not wrong, then at least not entirely correct.

I don't know exactly how a call coming into a air traffic controller sounds - i.e. if there's a bleep or something first. I'm thinking about situations where you're concentrating on multiple things already, and something needs to desperately grab your attention.

I'm pretty sure there is no beep or anything; there would be little value, and any such thing could risk masking the first portion of a transmission. That said, even when flying, with engine and propeller noise in the cockpit, I've never had any trouble telling when a transmission began or ended; it's pretty distinctive. I have had trouble hearing what people said on the radio once or twice when they wouldn't speak up, but in that case, repeating a single word a few times likely won't help much.

if this is just your unresearched perception it is not an answer. please provide sources for your statements.

If you repeat only twice and the receiver understand 2 different words (whatever the reason), the third repetition may help decide which one of the two possibility is the good one.

the reason for the repetition of mayday mayday mayday is for receiver of the messages can hear the callings, if the first mayday calling is breaking, the second mayday calling maybe be heard, and totally sure the third mayday the messages needs to be convey along with the mayday

This answer could be greatly improved by beginning each sentence with a capital letter and ending it with a period. I can't tell where the sentences here begin and end.

This doesn't answer why they say it ** 3 (three)** times and not four, tow, five, or seven times.


text:
The cost of maintaining VTOL devices
Which device for VTOL flight costs the most to maintain for a given number of flight hours?  A tiltwing mechanism?  A 2D thrust-vectoring nozzle (vectoring only between VTOL position and cruise position)?  A helicopter rotor mechanism?

Helicopters are definitely the cheapest way to get VTOL but to compare with other methods would be tough.  You'd have to get numbers from VTOL machine in production and service, like an Osprey, and compare with a helicopter in the same weight class.


text:
What is purpose of engine pylon airfoils on the Hondajet HA-420?
The engine pylons on the Hondajet are aerodynamically shaped so as to provide a lift force laterally and outwardly.

Engine pylon as viewed from rear

Engine pylon as viewed from front
Are these for lateral stability or drag reduction or both or other purposes?

seems like it tries to maintain a constant cross section area between the engine and aft fuselage. it's not meant to produce any force.

There is a pretty interesting write up on the pylon design here. According to that the shape was chosen for a number of reasons including flutter reduction, stall characteristics and wave drag reduction. There is also some more info here that briefly touches on the design.

The pylon writeup and all they looked at is quite interesting reading. Cabin size, wing laminar flow, stall characteristics, flutter, etc.  Too bad I can't unbolt the wing on my Cardinal, pull the engine, and replace them with a wing with 2 small jet engines!

@CrossRoads I think it would become an experimental but you could...

Yeah, that and the cost are a pretty big disincentive :) Plus my home field does not have jet fuel, only 100LL.

@CrossRoads: Most (possibly all) jet engines can run on 100LL, they just need to be inspected and maintained more frequently.

I would have to confirm but in conventional aircraft design the engines are usually in front of and below the main wing. Firstly this would allow a maximum of the fuselage to be utilized for cabin space. Also, having such highly isolated engine nacelles would provide low wave drag coefficients allowing for smooth and efficient flying at higher Mach numbers. The engine is quite large for the aircraft and because mounting engines aft on a small plane, and because it is too low to mount below the wing, it is probable that it was the only location to place the engine without making considerable compromises otherwise.
[Edit] Running a CAD model of the Hondajet through a flow sim, the upward pylons should also provide extra yaw moment stability.

Functioning as strakes?

Pretty much, yes.


text:
When a B-2 takes off, does it use some device to ionise the airflow in front it?
At takeoff, does the B-2 use some sort of ionization device in the leading edges of its wings?

While that's true the effect exists, it is unlikely it was used on the B-2. For those who want to dig into it: This is a serious topic of research, known as "ion wind" (also electrohydrodynamic thrust). If I'm not wrong this is used on this experimental aircraft.

I have never heard of an ionization device being used on an aircraft, but when I searched Google for "Northrop B-2 ionization", I actually found a reference for this:

Microwave frequencies emitted along the leading edge would readily ionize the approaching air and allow the B-2's high-voltage electric field to discharge a greater flux of positive ions. With increased ion currents, the B-2 would be able to generate a greater ion sheath space charge at a given velocity and thereby increase the electrogravitic and electrostatic thrust propelling the craft.

This quote is from the book Secrets of Antigravity Propulsion: Tesla, UFOs, and Classified Aerospace Technology by Paul A. LaViolette, which sounds a lot like pseudo-science and conspiracy theories. This page says about the author:

In addition, Paul LaViolette has developed a new theory of gravity that replaces the deeply flawed theory of general relativity.  Predicted from subquantum kinetics, it accounts for the electrogravitic coupling phenomenon discovered by Townsend Brown and may explain the advanced aerospace propulsion technology utilized in the B-2 bomber.

Putting the conspiracy theories aside, how much energy would be needed to ionize the air in front of an aircraft? It requires 14.5eV to ionize a single nitrogen atom (main component in air) and air has an average molar density of 28.97 g/mol resulting in a required energy per gram of air of
$$ E = \frac{14.5 \, \mathrm{eV} \times N_A}{28.97 \, \mathrm{g}/\mathrm{mol}} \approx 3.014 \times 10^{23} \, \mathrm{eV}/\mathrm{g} \approx 48.3 \, \mathrm{kJ}/\mathrm{g} $$
For comparison, jet fuel has an energy density of around 43kJ/g. So you need to burn about the same mass of jet fuel as air passes over the wings in order to ionize it. It goes without saying that this is not done on the B-2, nor any other aircraft.

This article about electrogravitics supports your claim about Paul LaViolette, on contrary regarding aircraft using ionic technology, this is a complete domain of research, with some results (e.g. this UAV by the MIT: "Air at the front of the wing is ionized by an electrical field near thin filaments of wire called emitters." It propulses a 2.5 kg mass at 17 km/h. For how long? they don't say).

@mins Nice find, I had never heard of that. It sounds like they do not ionize all of the air, just enough to accelerate air by bumping ions in it, so my calculation does not apply.

No, it doesn't.  Speculation about this was fueled by a Wikipedia circular citation.

"This is an encyclopedia not Usenet." LOL!


text:
Why did Lockheed Martin give the F-22 stealth fighter such small fuel tanks?
Why did Lockheed Martin give the F-22 stealth fighter such small fuel tanks while the F-35 got much more fuel capacity relative to its size and single jet engine?

The F-22 was developed in the 90's, primarily for use by the United States Air Force. This means it was designed to serve specific mission profiles. The F-35 however is going to replace the F-22 and serve all the air branches of the US Military. This means that it needed a broader mission profile. The last F-22 delivery was in 2016.
For the F-22 Raptor:

Range: >1,600 nmi (1,841 mi, 2,963 km) with 2 external fuel tanks
Ferry range: 1,740 nmi (2,000 mi, 3,220 km)
Combat radius:
     460 nmi (529 mi, 851 km) clean with 100 nmi (115 mi, 185 km) in supercruise
     590 nmi (679 mi, 1,093 km) clean subsonic
Service ceiling: 65,000 ft (20,000 m)

And for the F-35 Lightning II:

Range: 1,500 nmi (1,700 mi, 2,800 km) +
Combat range:
     669 nmi (770 mi, 1,239 km) - Combat radius
     760 nmi (870 mi; 1,410 km) - Combat radius (interdiction mission on internal fuel, for internal air to air configuration)
Service ceiling: 50,000 ft (15,000 m) +

You can see that the F-22 range (not the combat radius) is very similar to the F-35. The problem with the F-35 is that because it is available in VTOL configuration, it burns a lot more fuel. The VTOL F-35 (F-35B) only has a mission radius of 505nmi. This is because during VTOL operations the F-35 burns an incredible amount of fuel. So much so that a VTOL take-off usually requires mid-air refueling shortly after take-off.
Either way this boils down to a trade-off between how much gas to carry and how much weapons and other systems to stuff into the aircraft. The VTOL versions need much more complicated internal systems that take up a lot of space, so the range and payload suffer. Tanks can be mounted on external hard-points, but then radar cross-section becomes much bigger and maneuverability is decreased.
With mid-air refueling all the aircraft must really do is be able to go from a friendly area where the tanker is, complete the mission, and get back to the tanker, so range isn't as important as versatility.

"VTOL operations the F-35 burns an incredible amount of fuel" I always wonder how true this is. It feels more like VTOL limits the amount of fuel that you can take.

The F-35 was never designed to replace the F-22. It was designed as a replacement for the F-15, F-16, F-18, A-10 and probably other types as well to complement the F-22.

Wrong choice of words, it will take over for the F-22 since they are no longer delivering the Raptor.

Actually the reason for the lower combat radius in the F-35B is the lift fan kit decreases the total internal fuel volume of the airplane.

As the F-35 was intended to serve a ground support role, it needs "loitering capability", i.e. it needs fuel to stay in the combat zone, in case something pops up. The F-22 in contrast, was designed for interception and air superiority in mind. In both roles you either have a limited mission (interception), or tankers around (air superiority). Thus, you can live with smaller fuel capacity.


text:
Can an airline order a 777 with 787 flight deck avionics?
So an airline orders a 777, but instead of the cockpit in that, they request the 787 cockpit installed in their 777, is this even doable?

Is not possible to order a B777 with 787 flight deck style but... it's possible to order a B777x, that is developed exactly with this kind of flight deck.
In this other question this fact is highlighted, and if you want to see how is a B777x flight deck, you can see this video.

This is possible.  Aside from the question of how the new cockpit elements would fit into the older plane, the most important factors are how it affects performance and safety in the eyes of the regulators, and whether this is worth doing from a cost point of view.
A large transport aircraft has a Type Certificate (TC) from the regulator that oversees its development (FAA in the USA, EASA in the EU). All the development and testing includes a list of exactly what is installed and how it was tested to show that it is all safe to fly.  To modernise or replace some or all of a cockpit, even for a small part like a switch, the company that owns the TC has to prove to the regulator that all the safety and performance standards will still be met with the new (replacement) parts.  The proof and justification will be proportional to the severity of the change.  If the flight control computer for a Fly By Wire aircraft was being replaced with a new version, you can imagine there would be software changes, followed by flight testing and a lot of safety analysis to show everything worked as intended.
The more modern and complex the aircraft, the more expensive this process is, generally speaking. For the older MD-90s in the earlier example, it can be economically viable for a 3rd party to develop a Supplemental Type Certificate (even without the input of the original manufacturer) to add their equipment to the aircraft.  This is often done with older aircraft to modernise equipment, especially in order to meet new regulations.


text:
Where does one obtain a RAREP?
Where can I find Radar Weather Reports (RAREPs)? Are they still used? They are not anywhere on the aviationweather.gov website.

"follow up" to what?

follow up question to 'how does one obtain a RAREP?'

Doesn't "how" answer the "where"? Can you link the original question?

I understand why this question was initially unclear, but I'm not sure why it's unclear after Pondlife's edit. Can close voter please explain?

Coded RAREPs (Radar Weather Reports) and SDs (Storm Detections) may still be used to exchange data between radar stations, but for human users they seem to have been superseded by visual displays that provide a more human-friendly visualization of the same information, such as at http://www.aviationweather.gov/radar.  The PHAK you linked to (published in 2008) is likely out of date on this.  (But this is the most recent PHAK available.)
From http://weatherjackwilliams.com/answers-weather-radar/ :

The NWS Aviation Weather Center (AWC) doesn’t have any links to the
  coded SD/ROB reports, but does link to the Radar Summary chart, which
  is complied from these  reports.

This information is also incorporated into a standard weather briefing for a particular flight plan.  The DUAT system used to provide an "SD (Radar Weather Reports)" section in its briefings, but DUAT is no longer available.  DUATS instead has a section titled "Radar Summaries" in its briefings.

The system wouldn't let me include more than two links in my answer.  Here's the link to DUATS: https://www.duats.com/

Welcome to aviation.se Kiri!


text:
In the traffic pattern, what is the appropriate distance from the runway for the downwind leg?
Specifically for a piston general aviation aircraft, is there a recommended distance from the runway to fly the downwind leg? Does this change based on the speed of the aircraft?

I usually fly my down wind in the 172 about 1/2 mile from the runway. Really depends on TPA and speed, usually you can figure out based on your base to final turn.  If you are turning too hard,  increase the distance.

Related: Why is “dragging it in” considered bad in small aircraft, but fine in larger aircraft? and this one even has an answer which answers your question: What is a two- or three-mile base exactly?.

I don't think most people really think in terms of distance from the runway.  At least I don't: I just fly where it "looks right", which is something you pick up in training from an instructor who's telling you to fly the downwind where it "looks right".

Most instructors say that (in a low wing plane) you should see the runway on the tip of the wing or between the tip and 1/4 in the wing. AOPA has a nice over view of non towered airports here. This FAA brief states it should be flown 1/2 to 1 mile out (page 7-4 of FAA Airplane Flying Handbook, FAA-H-8083-3B).

This leg should be
  approximately 1/2 to 1 mile out from the landing runway,
  and at the specified traffic pattern altitude.

"Within gliding distance" is one common rule that many instructors teach. It would be embarrassing to have an engine failure in the pattern and not make it to the runway :-) More seriously, you tend to make a lot of configuration changes in the pattern so the risk of something going wrong is higher, therefore within gliding range is usually a good place to be.
That doesn't mean being in a position to glide the remaining downwind, base and final legs to land neatly on the numbers: it means gliding to somewhere on the runway you can safely land (or even to a taxiway if need be). (The FAA's commercial pilot test standards require the applicant to glide to a landing from the downwind leg starting at 1000 AGL.)
Of course, there are lots of variables and you may have to fly a wider (or tighter) pattern at certain times or at certain airports for any number of reasons: traffic, ATC instructions, noise abatement etc.

I don't quite follow this. On a normal circuit, I can land on the runway threshold only if I lose the engine shortly after turning base (i.e. where I'd close the throttle anyway). If the engine fails any time on downwind, if I want to land on the runway in the correct direction, I'm going to be touching down some distance along it - possibly too far along to make a safe roll-out. Being able to glide to the runway doesn't seem to be a huge advantage in that case.

@DanHulme I updated this based on chat comments

This is an old thread, but I gotta comment on "gliding distance from runway". Depending on aircraft, this might be very close to runway, assuming normal pattern altitude of 1000ft agl. Not that many common GA aircraft have good gliding properties, and considering all the risks involved in 180 turn at low alt + engine out, I personally would be hesitant turn back unless I had a DA40 or some other slippery plane under me...

There are multiple considerations, among them:

Other aircraft in the pattern (that may be slower or faster than you): you want to maintain your position, not getting too close to planes ahead of you, nor slowing down planes behind you.
The descent rate of your aircraft:  I was taught to descend 25% from TPA on downwind, 25% on base, and 50% on final. (typically from a 1,000 ft TPA, that is 250ft / 250ft / 500ft)
The turning rate of your aircraft: You want to make rectangular shaped patterns.  If you are too close, your patterns will be more oval shaped.  If you are too far, you will have a very long base leg.

If you lose an engine on downwind, you modify the rest of your pattern immediately to keep your aiming point on the windshield at the distance to your landing point. The pattern will no longer be square, but a continuous descending arc that ‘cuts the corners’ and terminates on a very short final to the runway.

This doesn't answer the stated question.

Welcome to AviationStackExchange. Although your answer describes a power out landing, it does not answer the specific question asked. Once you have enough reputation points, you can post this as a comment, instead. Otherwise, this answer may be deleted. A more appropriate answer would be to fly a standard traffic pattern far enough away to have a sufficient base leg, but close enough to perform a power off landing from your current altitude anywhere along the downwind leg.


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Why is this chart called a Short Field Effort Takeoff Ground Roll and not simply a Short Field Takeoff Ground Roll?
What does the word 'effort' mean in this context?

Although I don't know what it means, this is likely an expression used in tests and military operations. There is also the maximum effort take-off which leads to the associated minimum field length for maximum effort take-off, and the maximum effort landing. Other categories of efforts will include tactical effort from what I understand. You may see these wordings used here.

Without the "Effort" the name of the test would imply that the test was conducted on an actual short field.

That makes the most sense @A.I.Breveleri, thanks

I think it is used in the same meaning as the maximum effort takeoff/landing (similar to @mins comment above). Maximum effort takeoff is used to reduce the ground roll/obstacle clearance distance. Maximum effort landing (or assault landing, as it is called) is used to reduce the ground roll after landing. This is mostly used for military aircraft, which may have to operate from small, improvised forward air strips.
This is alluded to in the PA-44-180 manual:

In certain short field takeoff efforts when the shortest possible ground roll and the greatest clearance distance over a 50 ft. obstacle is desired, a flap setting of 25° is recommended.

This can also be figured out from the charts themselves. For Pressure altitude of 680', OAT of 8$^{\circ}C$, 8kt headwind and 3430 lb TOW, the normal TO roll is 920', while the short filed effort TO roll is only 800'. For the same specifications, the total distance over a 50' barrier using normal procedures is 1750', while using short field effort, it reduces to 1280' (All figures from the manual).
You can see a C130J demonstrating max-effort TO and landing here.


text:
What is the difference between a nacelle and a cowling?
I see these terms used almost interchangeably. To my understanding they both refer to the covering of an engine. Is there a technical difference between the two?

The definition of a nacelle refers to the housing of anything on the outside of an aircraft. Engines are the most common thing in these housings.

a streamlined housing or tank for something on the outside of an aircraft or motor vehicle.

The definition of a cowling is specifically a removable cover of the engine.

the removable cover of a vehicle or aircraft engine.

So a nacelle refers to the whole covering of an engine that is outside the plane, typically on the wing. The cowling would just be the removable part of this cover. As Jan Hudec commented, engines mounted in the nose, as is typical in smaller aircraft, would have a cowling to allow access and cooling to the engine, but technically not a nacelle, since the covering would be part of the fuselage.

On the other hand, nose-mounted engine has cowling, but it is not in a nacelle.

Also worth bearing in mind that cowlings are often a critical component in the cooling of aircooled engines - aircooled engines on cars will also have cowlings to direct airflow.

The nacelle is a housing that is separate from the fuselage, that holds something, usually engines or some other equipment in an aircraft. The following figure shows some of the engine nacelles.

Source: adg.stanford.edu
A cowl or cowling is any part of the aircraft (or engine nacelle) that can be opened or removed (for inspection etc.). The following image shows cowlings in a nacelle.

Source: compositesworld.com
These are maintenance cowlings. Another type of cowlings (like NACA cowlings) serve to direct the airflow into the engine.

Nacelle comes from the french word "nacelle" which is the gondola or wicker basket suspended beneath a balloon. So, by analogy, many things that are outside the body of an aircraft, like the compartments that house the engines, can be called nacelles. A cowling is the covering of a vehicle's engine even if that motor is not inside a nacelle.

Nacelles usually have structural components like frames,formers and stringers  due to there sizes, and are found mostly on turbine engines. while Cowlings don't always have structural components and are usually smaller in size compare to Nacelles as seen on piston engine aircraft.


text:
What are the differences between these IFR Low Altitude Chart Navaid Symbols?
Below are three NAVAID chart symbols. There is almost no explanation on the aeronautical chart user's guide. It even says that a navaid with an FSS will be shaded but the third box has an FSS and it isn't shaded!
I would like to understand what everything on each of these boxes stands for.

its worth noting that LAA were transitioned to "remote airport advisories" when Lockheed took the FSS contract and consolidated 58 FSS into 5. They are now proposing to eliminate RAAs https://www.federalregister.gov/articles/2015/06/30/2015-15949/discontinuation-of-airport-advisory-service-in-the-contiguous-united-states-puerto-rico-and-hawaii

The shadow in the NAVAID box indicates that the NAVAID and FSS have the same name, as in your top image. If they are different, the FSS name is given in brackets below the NAVAID box, as in your bottom image. If the FSS is not available, a thin line box is used for NAVAID (without brackets at the bottom), as in the middle figure.
FAA Aeronautical Chart User's guide should help you understand it better.

Image from FAA Aeronautical Chart User's guide

Your top example would have an FSS with the same name as the Navaid, while your bottom example would have an FSS (with a different name) that controls that Navaid -- i.e. can use it to receive & transmit, even though it isn't co-located.  The presence of either the shadow OR the FSS name (different from the Navaid's name) in brackets underneath will tell you that there is the ability to contact an FSS at that Navaid; without the shadow & with the FSS name underneath, the FSS is physically located elsewhere.  This link (select the "IFR Symbols" tab) has the following graphic:

In this example (halfway down), the Jonesboro FSS controls the Pine Bluff VOR and can use 122.6 to talk to aircraft close to Pine Bluff.  In the example directly above that one, there is a remote transmitter (with no associated Navaid) that Jonesboro FSS can use to talk to aircraft on 122.55.  Either way, you're talking to Jonesboro FSS (as there is no "Pine Bluff FSS").
In the top example in that graphic, you'd be able to talk to Wichita FSS on 122.65 using an antenna approximately at the ICT VOR -- FSS name matches the Navaid name.

In the example, why does the El Dorado ELD have a 123.6 and a 122.65? Why are there two frequencies? Can you talk to the FSS on both frequencies?

@jskypilot  Yes, you can. Looks like 123.6 is a "local airport advisory" frequency, so they can give you winds & such for the local field. The other frequency is for traffic passing by that's getting updates on things other than the local airport itself. They probably use separate frequencies to avoid congestion. I think (others can chime in) that the "local airport advisory" frequency is essentially CTAF with the FSS there to provide conditions (but not control the traffic). Better to separate out "update weather for my destination" radio traffic from the calls by pilots in the pattern.

authors: Артем Синюков


text:
How do you know if a VOR is High, Low, or Terminal?
Is there any way of telling on both a VFR and IFR chart what type of VOR we are looking at?

Related: http://aviation.stackexchange.com/questions/24040/when-is-a-vor-shown-on-maps

The range of the VOR is included in the Airport/Facility Directory data under the name class
From A/FD legend:

Example:

Service volume for each class:

One thing that can trip you up when looking for the info is that VORs which are located on an airport do not have a separate entry but are shown at the bottom of information for the airport in the 'Radio Aids to Navigation' section.

Typically terminal VOR's do not have compass roses around them if they are strictly terminal VOR's. I can't find an example of one so I don't have an image for it.
Edit I found an example:

Source: SkyVector
The DEN VOR has no compass rose, so its either a terminal VOR or they omitted the compass rose for clarity. There are two other VOR's in close proximity, MILE HIGH on the North East side of the field and Falcon to the east of Buckley AFB. According to AirNav NavAid Info its a high VOR.
As far as high/low VOR, one way to tell is to look at the High/Low enroute IFR charts.
For example, here is a portion of a low-enroute IFR chart:

Source: SkyVector
You can see two VOR stations on here labeled Minot Intl and Devils Lake Rgnl with a victor airway between them (V430).
Here is the same area from the high enroute IFR chart:

Source: SkyVector
You can see that the VOR symbol around Devils Lake Rgnl has disappeared and (although its difficult to see) the VOR symbol has also disappeared. NavAid Website lists DVL (Devils Lake) as a LOW VOR and also lists MOT (Minot International) as a HIGH VOR.
There is no differentiation between the VOR high/low symbols on a VFR chart because low altitude VOR's can serve aircraft up to 18,000 feet where you would need to file an IFR flight plan anyway, so all VOR's regardless of high/low are available to VFR flights.
Putting it another (technical) way is that high/low VOR's have the same service volume for VFR and low-enroute IFR flights, so they do not need to be distinguished on VFR or low-enroute IFR charts.

This guy got a bunch of downvotes for saying exactly what you said so I am just trying to find an official source. http://www.askacfi.com/9869/how-can-i-determine-if-a-vor-station-is-h-l-or-t.htm

I think that guy got downvotes because people may have misunderstood when he said that you know if its high or low by it having a compass rose, you know if its a terminal one by it not having a compass rose, but both high and low have compass roses on them (well, not always, but typically). There are cases where a high/low VOR does not have a compass rose usually to reduce clutter on the VFR chart near an airport, which makes it almost indistinguishable from a terminal VOR.

@jskypilot I edited my answer with an example of a VOR that does not have a compass rose (first image).

From the chart you can understand what type of VOR is that  But there are also other ways . By checking the frequency band you can also understand the type of that VOR.   There are basically two types of them and they are Terminal VOR(TVOR) and Airway VOR. The whole VOR frequency range is VHF-108 to 117.95MHz.  ILS frequency shares some portion of the TVOR. The terminal VOR are mainly of low and the airway VOR are mainly of high type.

TVOR frequency band are from 108.00 to 112.00MHz. In details, TVOR uses even first decimal and even first decimal +50KHz upto 112MHz. Like 108.00MHz, 108.15MHZ, 108.20MHz, 108.25MHz etc
and the ILS uses odd first decimal and odd first decimal +50KHz upto 112.00MHz. Like 108.10MHz, 108.15MHz,108.30MHz, 108.35MHz etc.
Airway VOR uses the remainder of the frequency band 112.00MHz to 117.95MHz.
other than this you can understand the VOR type from the chart the people has already shown.


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What is radar minima?
I was studying the Aeronautical Chart User's Guide and I came across the term 'radar minima' several times under the graphics depicting charted airports.

Blue – Airports with an Instrument Approach Procedure and/or
  RADAR MINIMA published in the high altitude DoD Flight
  Information Publications (FLIPs)
Green – Airports which have an approved Instrument Approach
  Procedure and/or RADAR MINIMA published in either the
  U.S. Terminal Procedures Publications (TPPs) or the DoD FLIPs
Brown – Airports without a published Instrument Approach
  Procedure or RADAR MINIMA

The FAA Pilot/Controller glossary doesn't define the term "radar minima", although the term "minima" redirects to "minimums". Its possible this either refers to radar separation minimums or minimum vectoring altitude (MVA), but I can't verify that.

(US) Radar minimums are published in the TPP. Here is a snapshot for Elmendorf Anchorage AFB, available on FlightAware.

Published minimums for an ASR or PAR approach.
An ASR is essentially a non-precision approach with an MDA, while a PAR is a precision approach (found almost exclusively at military fields) with minimums of 200 and 1/2.

you can always ask for a "no gyro" practice approach. the ex-military controllers love them, and I think they're fun to do


text:
Where can I find FAA procedure amendments?
I'm looking at the IFR Takeoff Minimums and (Obstacle) Departure Procedures for Goodyear, AZ (KGYR). It says:

Takeoff Minimums and (Obstacle) Departure Procedures AMDT 1 14317
  (FAA) Departure Procedure: Use POTER RNAV Departure

I would like to read this amendment but my Google-Fu is failing me. Help?

As far as I know, you're looking at them: that number is telling you that the current procedure is AMDT 1 14317. Have a look at the other procedures throughout the same document and you'll see they're all numbered in a similar way.
In your example, AMDT 1 14317 is Amendment 1, made on November 13, 2014. The date format is a Julian date or, if you prefer, YYDDD: it's the 317th day of 2014, i.e. November 13, 2014. The format is explained in the FAA's FAQ on obstacle data (and it's mentioned in other documents).
If the procedure has never been amended it's marked ORIG, e.g. at Beaver Muni (U52):

BEAVER, UT
  BEAVER MUNI (U52)
  TAKEOFF MINIMUMS AND (OBSTACLE) DEPARTURE PROCEDURES
  ORIG 07242 (FAA)
  TAKEOFF MINIMUMS: [...]

@mins I updated the answer


text:
Are there any operational, combat capable multicopter drones (as of 2019)?
Are there any small operational military drones with any form of weapons system on board, as of 2019?
I'm basically referring to a more powerful, more sophisticated and refined version of something similar to this:

If there isn't its only a mater of time

That kid's dad is going to be really sorry that he didn't supervise his son more closely.

Interesting links: https://www.google.com/amp/s/www.popularmechanics.com/military/aviation/amp26414352/kalashnikov-kub-bla-drone/. https://youtu.be/1zN33m3Dq6Y


text:
How fast is it safe to eject from an F-16?
What is the limit of the ACES II for the F-16, in terms of altitude and airspeed for safe ejection?
The following video tells the story of an F-15 pilot who ejected at supersonic speed and barely survived.

In general, it also seems that ejection, even under controlled circumstances is not a trivial matter:

I'm curious what the safe ejection speed and altitude is for an F-16, with the ACES II ejection seat.
I've read about the ACES II here https://en.wikipedia.org/wiki/ACES_II and watched a documentary about ejection seats in general.
It seems to me that supersonic ejections should be done with some form of capsule to protect the pilot, and not allow the pilot to be exposed directly to the atmosphere.
I can imagine that the manual for the F-16/ACES II provides some kind of graph that describes the safety of ejection as a function of airspeed and altitude, assuming the same orientation of the plane (although the ACES II is known for being able to eject safely with the plane inverted, with a certain minimum altitude).
As a bonus question: What does the F-16 manual specify as a procedure, if ejection is not safe? Does the manual call for the pilot to eject anyway, at any speed, and pray for the best? Or does it call for trying to mitigate the situation without ejection, when this is not safe?

I imagine one would eject no matter the risks... given one usually only thinks about ejecting when remaining in the aircraft implies imminent death.

You eject when the alternative is crashing.  Ejecting is always safer than crashing.  Neither is considered "safe".

True 'nuf both comments above, but all ejection seat aircraft have a controlled ejection procedure if the aircraft is controllable, yet doomed, and death is not mere seconds away.  Time permitting, to reduce risk perform as much of the following as possible:  Level the wings and arrest the rate of descent, slow to minimum controllable airspeed, squawk emergency and/or get out a mayday call, point the aircraft towards an unpopulated area, jettison the canopy, assume the proper body position, eject.

Top Gun had an excellent illustration of why even ejecting at slower speeds is dangerous

@CarloFelicione disagree on dupe, this is a lot more specific to airspeed.

Related: https://aviation.stackexchange.com/questions/68529/what-are-the-ejection-injury-and-fatality-rates